Abstract

Background

Parenteral opioids are used for pain relief in labour in many countries throughout the world.

Objectives

To assess the acceptability, effectiveness and safety of different types, doses and modes of administration of parenteral opioids given to women in labour.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register (30 April 2011) and reference lists of retrieved studies.

Selection criteria

We included randomised controlled trials examining the use of intramuscular or intravenous opioids (including patient controlled analgesia) for women in labour. We looked at studies comparing an opioid with another opioid, placebo, other non-pharmacological interventions (TENS) or inhaled analgesia.

Data collection and analysis

Main results

We included 57 studies involving more than 7000 women that compared an opioid with placebo, another opioid administered intramuscularly or intravenously or compared with TENS to the back. The 57 studies reported on 29 different comparisons, and for many outcomes only one study contributed data. Overall, the evidence was of poor quality regarding the analgesic effect of opioids, satisfaction with analgesia, adverse effects and harm to women and babies. There were few statistically significant results. Many of the studies had small sample sizes, and low statistical power. Overall findings indicated that parenteral opioids provided some pain relief and moderate satisfaction with analgesia in labour, although up to two-thirds of women who received opioids reported moderate or severe pain and/or poor or moderate pain relief one or two hours after administration. Opioid drugs were associated with maternal nausea, vomiting and drowsiness, although different opioid drugs were associated with different adverse effects. There was no clear evidence of adverse effects of opioids on the newborn. We did not have sufficient evidence to assess which opioid drug provided the best pain relief with the least adverse effects.

Authors' conclusions

Parenteral opioids provide some relief from pain in labour but are associated with adverse effects. Maternal satisfaction with opioid analgesia was largely unreported but appeared moderate at best. This review needs to be examined alongside related Cochrane reviews examining pain management in labour. More research is needed to determine which analgesic intervention is most effective, and provides greatest satisfaction to women with acceptable adverse effects for mothers and their newborn.

Plain language summary

The use of opioid intramuscular and intravenous pain relieving drugs in labour

Pain during labour is normal and its management is influenced by an interaction between a woman's mental and emotional state and the physiological changes that occur during labour. The use of pain-relieving drugs during labour is now part of standard care in many countries throughout the world. In recent years, many women in Western countries have chosen to have epidural analgesia to relieve pain. However, some women prefer not to have an epidural, or in some settings an epidural is not available. In many maternity units intramuscular injections of opioid drugs are widely used for pain relief in labour and options for intravenous infusions may also be available. The opioid drugs used include pethidine (also known as meperidine or demerol), diamorphine, nalbuphine, butorphanol, meptazinol, pentazocine, fentanyl and tramadol, and are relatively inexpensive. It is not clear how effective these drugs are, which opioid is best, and how unpleasant side effects (such as vomiting or sleepiness) or harm to women or their babies can be avoided.

We included 57 randomised controlled trials involving more than 7000 women that compared an opioid with placebo, another opioid or transcutaneous electrical nerve stimulation (TENS). Overall, our findings indicated that opioids provided some pain relief during labour, although substantial proportions of women still reported moderate or severe pain. Opioid drugs were associated with nausea, vomiting and drowsiness, and different types of opioids were associated with different side effects. There was no clear evidence of adverse effects of opioids on the newborn. Maternal satisfaction with opioid analgesia was largely unreported but appeared moderate. We did not have sufficient evidence to assess which opioid drug women were most satisfied with, or which provided the best pain relief with the least side effects for mothers and babies.

In this review the 57 studies reported on 29 different comparisons, and for many outcomes only one study contributed data. We did not examine the effectiveness and safety of intramuscular or intravenous (parenteral) opioids compared with other pharmacological methods of pain relief in labour (such as epidural analgesia) and this review needs to be examined alongside related Cochrane reviews. As parenteral opioid drugs are so widely used it is important that more research is carried out so that women can make informed choices about these forms of pain relief.